Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 38221 — Big Sandy, TN

ZIP code 38221 (Big Sandy, Benton County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 8 and the first fall frost October 29.

Where ZIP 38221 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone7b5 to 10 °F

Coldest night−15 to −12.2 °C

Last frostApr 8

First frostOct 29

2012 zone7a

Was 7a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Big Sandy, TN…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Big Sandy, TN

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 8median — 50% chance of a later frost

Safe for tender plantsApril 23only 10% chance of frost after

First fall frostOctober 29median — 10% chance by Oct 14

Growing season202 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 28 and returns around November 8.

From the NOAA station Big Sandy, TN — 2 miles away, elevation 364 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 38221

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 25 – Mar 11

SpinachSow outdoors · Feb 25 – Mar 18

Broccoli, cabbageStart indoors · Jan 28 – Feb 11

Broccoli, cabbageTransplant · Mar 18 – Apr 1

Onion setsPlant outdoors · Mar 11 – Mar 25

PotatoesPlant outdoors · Mar 18 – Apr 1

LettuceSow outdoors · Mar 11 – Mar 25

Carrots, beetsSow outdoors · Mar 18 – Apr 1

TomatoesStart indoors · Feb 11 – Feb 25

TomatoesTransplant · Apr 15 – Apr 29

Peppers, eggplantStart indoors · Jan 28 – Feb 11

Peppers, eggplantTransplant · Apr 22 – May 6

BeansSow outdoors · Apr 15 – Apr 29

Sweet cornSow outdoors · Apr 15 – Apr 29

Cucumbers, squashSow outdoors · Apr 15 – Apr 29

Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17

GarlicPlant cloves · Oct 15 – Nov 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Oct 29) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 38221 came on Feb 25 — about the same time as the 1991–2020 average (Feb 25).

average
Feb 252026
Feb 25

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 7b in Tennessee

566 plants native to the lower 48 states, recorded in Tennessee, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Big Sandy, TN.

Soil in Big Sandy, TN

The soil mapped at the center of ZIP 38221 is Lax — silt loam, moderately well drained.

TextureSilt loama good balance for most vegetables

pH5.4strongly acidic; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter1.25%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Lax silt loam, 5 to 12 percent slopes, eroded.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 38221; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Big Sandy, TN

Summer high88 °Faverage high, July

Winter low29 °Faverage low, January

Hot days52days a year at 90 °F or more

Freezing nights80nights a year at 32 °F or less

Growing degree days4,704base 50 °F — the season’s usable heat

Longest day14 h 38 mindaylight on June 21

Shortest day9 h 41 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation55.1 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Big Sandy, TN (2 mi away); precipitation: Big Sandy 0.6 Ne, TN (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7b.

382567b

Springville, TN · 7 mi

Mansfield, TN · 14 mi

383207b

Camden, TN · 14 mi

371787b

Tennessee Ridge, TN · 15 mi

Tennessee planting zones →

Questions about 38221

What planting zone is ZIP code 38221?

ZIP code 38221 (Big Sandy, TN) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Big Sandy, TN?

The median last spring frost (32 °F) near 38221 is April 8; after April 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Big Sandy station.

When is the first frost in Big Sandy, TN?

The median first fall frost near 38221 is October 29, giving a median frost-free growing season of 202 days.

When should I plant tomatoes in 38221?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 38221 get?

About 55.1 inches of precipitation a year (NOAA 1991–2020 normals, Big Sandy 0.6 Ne station).

How hot do summers get in Big Sandy, TN?

The average high peaks at 88 °F in July, with about 52 days a year at 90 °F or more.

What kind of soil does 38221 have?

The USDA soil survey maps Lax at the center of ZIP 38221: silt loam, moderately well drained, pH about 5.4 (strongly acidic).

Did spring come early in Big Sandy, TN in 2026?

Spring leaf-out near 38221 came on Feb 25 in 2026, about the same as the 1991–2020 average (Feb 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Big Sandy, TN?

Intermediate onions: the longest day near 38221 is 14 h 38 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 38221 change?

Yes. The 2012 USDA map put 38221 in zone 7a; the 2023 map puts it in zone 7b. The newer map uses 1991–2020 data and more weather stations.